The development of safe medical syringes and procedures for using them have long been a matter of concern, especially to the medical field. Many medical procedures, such as the transfusion of blood and the administration of insulin in some circumstances, require the use of needles and syringes, with their attendant hazard of accidental scratch or puncture. Recently, the risk has increased dramatically of contracting virulent and fatal or near-fatal infections during legitimate medical procedures using needles, and the general public as well as the medical profession has demanded safer products and procedures.
Efforts to minimize the risk of accidental infection have been made for several decades. Some representative efforts are:
La Marche U.S. Pat. No. 1,921,034 discloses a protector case for a syringe of conventional type, which allows for the needle to be exposed the correct amount for the type of shot to be given, and to be retracted after use to protect others from being accidentally punctured thereby.
Bastien U.S. Pat. No. 2,571,653 discloses a syringe body encased in a slidable protector case, having built-in detents to hold the needle in a retracted position prior to and following use, while permitting the needle to be exposed the correct length for the purpose.
Tschischeck U.S. Pat. No. 2,586,581 discloses an add-on magnifying attachment for syringes. It has no relevance to the present invention, except to disclose one means of making the scale more readable and the dosage more accurate.
Norgren U.S. Pat. No. 3,943,927 discloses an injection device to be carried by persons having allergic reactions to insect or snake bites, or bee stings, where antitoxins or other emergency remedies need to be administered immediately under conditions of great physical or emotional stress. It has little relevance to the present invention.
Ethington U.S. Pat. No. 4,018,223 discloses a tactile-detent dosage metering device for use by persons with impaired vision.
Chen U.S. Pat. No. 4,728,321 discloses a means to render a needle unfit for further use, by placing thereon a syringe cap and permanently cementing it in place.
Bogan U.S. Pat. No. 4,738,663 discloses a removable protective cover for the needle of a syringe.
Leopoldi et al U.S. Pat. No. 4,743,234 discloses a syringe with needle shield which provides protection to users when the shield is moved to cover the needle. The mechanism provides detent positions in both extended and retracted positions, but not a permanently locked position.
None of the above references disclose, either singly or in combination, the structure and attendant features of the present invention.